820-2936 PP3V42 being pulled down.

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

Hi Mon2,

The parts are yet to arrive. But something happened. I reballed the SMC, plugged in the charger and now I have a green light. But PPBUS_G3H is still 1.09v.

[mon2]

Re: 820-2936 PP3V42 being pulled down.

Remove the fuse on ppbus_g3h.

Power up again. Check the voltage to ground of ppbus_g3h at the isl side.

What is the voltage reading?

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

Hi mon2,

The diode mode reading to gnd is 0.431v.

[mon2]

Re: 820-2936 PP3V42 being pulled down.

No, not the diode mode reading but actual voltage reading.

Remove all power.

Meter in DC volts scale.

Attach the power adapter -> measure the voltage to ground of PPBUS_G3H on the ISL side. Measure on the removed fuse PCB pad.

Do you now see a proper voltage without the fuse?

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

Aaah.Its still 1.019V. Is ISL6259 (u7000) to blame for?

[mon2]

Re: 820-2936 PP3V42 being pulled down.

Confirm the resistance to ground of this same pin - with no power to the board.

After this test, yes, suggest that you replace the ISL component and test again - without the fuse to confirm the PPBUS_G3H is within a valid range.

Then add the fuse back and continue to test.

Update - do also test the switching mosfets that are linked to this power rail.

Do this with resistance checks - with no power.

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

I think SMC is functioning due to the green light and the SMC_ONOFF_L is up now. But PPBUS_G3H is still 1.019V.

[mon2]

Re: 820-2936 PP3V42 being pulled down.

Check the voltage to ground of Q7030, DRAIN pin. This is the high side mosfet and should be with a higher voltage = adapter voltage.

That is, Q7030 and Q7035 work together to create the PPBUS_G3H rail. If either is defective, the voltage will be low. The ISL is the driver for each of these mosfets.

Confirm the resistance of each mosfet - with no power:

source & drain
source & gate
gate & drain

Check for a low resistance. If the resistance is low, the mosfet could be defective. If the mosfets are fine, the ISL is a key suspect.

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

Hi mon2,

I have already ordered ISL6259 and is yet to arrive. It should reach me within the next 2 - 3 days. In the meantime, I shall post the resistance at the high side mosfet.

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

OK.
The voltage to ground of Q7030 on the drain pin is 1.019V.

Resistance from Source to Drain (Q7030) - Around 5.8 MOhms
Resistance from Source to Gate (Q7030) - Around 6.4 Ohms
Resistance from Gate to Drain (Q7030) - Around 5 MOhms

Resistance from Source to Drain (Q7035) - Around 17.5 KOhms
Resistance from Source to Gate (Q7035) - Around 5.16 KOhms
Resistance from Gate to Drain (Q7035) - Around 4 MOhms

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

Hi mon2,

The results are above. Please advise.

[mon2]

Re: 820-2936 PP3V42 being pulled down.

Resistance from Source to Drain (Q7030) - Around 5.8 MOhms
Resistance from Source to Gate (Q7030) - Around 6.4 Ohms
Resistance from Gate to Drain (Q7030) - Around 5 MOhms

Is this 6R4 ohms or should it be 6.4 Mohms?

[mon2]

Re: 820-2936 PP3V42 being pulled down.

From post #21

I reballed the SMC, plugged in the charger and now I have a green light. But PPBUS_G3H is still 1.09v.

The voltage to ground for PPBUS_G3H is this low @ 1.09v ?

If yes, remove the fuse on this rail @ F7040.

Measure the voltage to ground @ F7040 pad # 1.

Do you still see this low voltage?

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

From post #21



The voltage to ground for PPBUS_G3H is this low @ 1.09v ?

If yes, remove the fuse on this rail @ F7040.

Measure the voltage to ground @ F7040 pad # 1.

Do you still see this low voltage?

Hi mon2,

Yes. It is still 1.09V on F7040, pad 1.

[mon2]

Re: 820-2936 PP3V42 being pulled down.

Originally at the start of this thread, the ppbus_g3h voltage was higher - right?

Need to check what was reworked.

Check the voltage to ground of the i2c lines - SCL and SDA on the isl regulator linked to this power rail.

Also check the mosfet details from post #32. Remove all power on checking resistance.

If the isl was replaced, flux and reflow it. Low air pressure.

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

Originally at the start of this thread, the ppbus_g3h voltage was higher - right?

Need to check what was reworked.

Check the voltage to ground of the i2c lines - SCL and SDA on the isl regulator linked to this power rail.

Also check the mosfet details from post #32. Remove all power on checking resistance.

If the isl was replaced, flux and reflow it. Low air pressure.

Hi mon2,

I will check the voltage of the i2c lines and post it later on today. It is very strange as you said. But there was no green light at all during the start. Now we have it and the PP3V42 has come up and looks like SMC is functioning now, atleast partially.

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

Is this 6R4 ohms or should it be 6.4 Mohms?

Hi mon2,

The voltage to ground on R5280 & R5281 is 3.420V. The resistance between source and gate on Q7030 is 6.4 Ohms.

[mon2]

Re: 820-2936 PP3V42 being pulled down.

With such a low resistance reading, q7030 looks to be shorted. Carefully remove this part and confirm the resistance when the mosfet is on your work table.

The reading should be hundreds of Kohms or higher.

Be sure your meter scale is correct or is it autoranging?

Perhaps you can post a picture of the front face of your meter while taking this measurement as a final check?

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

Hi mon2,

I did check Q7030 after removing it. The resistance between source and gate on Q7030 is 16.19kOhms. I reinserted the mosfet again and the reading is the same. Might have been a dry joint/soldering.

[mon2]

Re: 820-2936 PP3V42 being pulled down.

At 16k ohms, the reading very low. Suggest to replace this mosfet.

Continue to check other mosfets as well in this area.